The present invention relates to signal transmitting/receiving systems and methods, signal transmitting apparatuses and methods, signal processing apparatuses and methods, recording media, and programs. Particularly, the present invention relates to a signal transmitting/receiving system and method, a signal transmitting apparatus and method, a signal processing apparatus and method, a recording medium, and a program that allow signals to be transmitted/received quickly and reliably without being affected by other electronic apparatuses.
Television receivers that are currently used have attached remote controllers so that users can input various instructions by operating the remote controllers.
FIGS. 1A to 1D are timing charts of remote control signals generated by a remote controller. As shown in FIG. 1A, a command is output three times in total by a rate of once per each command interval Ti. The command interval Ti corresponds to the period of one field of a television receiver, i.e., 1/60 second in the case of NTSC.
As shown in FIG. 1B, a start bit Sb is disposed at the beginning of the command, and an end bit Eb is disposed at the end of the command. Between the start bit Sb and the end bit Eb, data and parity Pt are disposed.
The data is binary data composed of bits representing logic “0” or logic “1”. As shown in FIG. 1C, logic “0” is represented by a signal having a length of time T0, and logic “1” is represented by a signal having a length of time T1. As shown in FIG. 1D, a carrier having a length of a carrier time Tc is disposed at the beginning of a bit.
The frequency of the carrier has hitherto been 38 kHz to 40 kHz. However, for example, in order to quickly move a cursor on a television screen, a frequency of 455 kHz has recently been proposed.
FIG. 2A shows driving signals of a plasma display (PDP). Referring to FIG. 2A, by a period of a field time Tf, pulses are supplied during a predetermined period in the field time Tf. The brightness is increased as the number of pulses is increased. As shown in FIG. 2B, each of the pulses is composed of a carrier having a length of a carrier pulse time Tp and a frequency of 250 kHz.
FIG. 3 shows the frequency spectrum of the driving signals for the plasma display, shown in FIGS. 2A and 2B. The spectrum has a fundamental frequency of 250 kHz and odd harmonic components.
FIG. 4 shows the spectrum of electroluminescence of the plasma display. The plasma display performs fluorescence emission by ultraviolet rays having wavelengths in the vicinity of 400 nm, so that it generates parasitic emissions having wavelengths of 850 nm or longer, as shown in FIG. 4.
Thus, for example, when a remote control signal represented by a binary code composed of a combination of time T0 and time T1 is generated in the proximity of a plasma display as shown in FIG. 5A, if parasitic emissions of the plasma display occur substantially at the same timing as shown in FIG. 5B, the parasitic emission components of the plasma display are superposed on the remote control signal as shown in FIG. 5C, so that the remote control signal is interfered with. As a result, although a binary code of logic “0” and logic “1” is supposed to be represented by time T0 and T1, for example, the length of time T0 representing logic “0” is detected to be shorter than its actual length, as shown in FIG. 5C. This inhibits the bit from being recognized as logic “0”. This problem similarly occurs for logic “1”.
This indicates that the use of the remote controller is inhibited in the proximity of the plasma display.
In view of this problem, for example, according to techniques proposed in Japanese Unexamined Patent Application Publication No. 8-294180, a remote controller is physically connected to a plasma display via an optical fiber so that remote control signals are fed to the plasma display via the optical fiber.
However, when a remote controller is connected to a plasma display via an optical fiber as described in Japanese Unexamined Patent Application Publication No. 8-294180, the range where the use of the remote controller is allowed is restricted, and the optical fiber can be an obstacle. This causes inconvenience in living environment.